programming

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Programming
TBE 540
Farah Fisher
Objectives

After viewing this presentation, the
learner will be able to…
• Given a task, create pseudocode
• Given pseudocode, create a flowchart
• Define/describe these terms: program,
compile vs. interpret, loop, variable, function,
syntax, code, debug, IF THEN ELSE
What is programming?



Series of instructions to a computer to
accomplish a task
Instructions must be written in a way the
computer can understand
Programming languages are used to
write programs
What is programming?


Once the code (language) of a program
has been written, it must be executed
(run, started).
You may need to type the name of the
program to start it, or use a word like
RUN and the name of the program (in
the old days, anyway).
What is programming?


Some programming languages (like Java
or C++) require the code to be compiled
(translated to binary) before it can be
started.
Others (like JavaScript) are interpreted,
meaning that each command is
translated separately when the program
is started.
What is a programming
language?


Set of commands that a computer has been
“taught” to understand
Languages that look like “machine code” (e.g.,
82A8: jsr r5,@#82AE 82AC: sob r0,8296) are used for…
•
•

Writing games
Writing application programs (like Excel)
Other languages look like English (“high level,”
e.g., PRINT “HELLO”)
•
•
•
Logo
JavaScript
And many more
What does programming
look like?

Here are some examples of an instruction to
print the word HI
•
•
•
•
•
•
•
•
Logo
JavaScript
FORTRAN
BASIC
COBOL
C++
Pascal
Assembly
Language
PR [HI]
alert(“HI”);
PRINT “HI”
PRINT “HI”
DISPLAY ‘HI’.
printf(“HI”);
WRITELN(‘HI’);
XPRNT MESSAGE1
MESSAGE1 DC ‘HI’
How do you write a program?




Decide what steps are needed to complete
the task
Write the steps in pseudocode (written in
English) or as a flowchart (graphic symbols)
Translate into the programming language
Try out the program and “debug” it (fix if
necessary)
What is pseudocode?



List of steps written in English
Like the instructions for a recipe
Must be in the right sequence
• Imagine saying “bake the cake” and then “mix
it up”
Sample Pseudocode


Task: add two numbers
Pseudocode:
• Start
• Get two numbers
• Add them
• Print the answer
• End
What does a flowchart look like?

The pseudocode from the previous slide
would look like this as a flowchart:
Start
Print answer
Get 2 numbers
End
Add them
What are those funny symbols?

START/END

INPUT/OUTPUT

PROCESS

DECISION
What are those funny symbols?


START/END
Used at the beginning
and end of each
flowchart.
What are those funny symbols?
What are those funny symbols?


INPUT/OUTPUT
Shows when
information/data comes
into a program or is
printed out.
What are those funny symbols?
What are those funny symbols?


PROCESS
Used to show
calculations, storing of
data in variables, and
other “processes” that
take place within a
program.
What are those funny symbols?
What are those funny symbols?


DECISION
Used to show that the
program must decide
whether something
(usually a comparison
between numbers) is
true or false. YES and
NO (or T/F) branches
are usually shown.
X>7?
N
Y
Another Sample:
Calculating Age

Pseudocode:
• Start
• Get year born
• Calculate age
• Print age
• If age > 50 print OLD
• End
Another Sample:
Calculating Age
Start
Get yr

Flowchart
• Start
• Get year born
• Calculate age
• Print age
• If age > 50 print OLD
• End
Calc age
Print age
OLD
Y
Age>50?
N
End
Elements of a Program


All programming languages have certain features in
common. For example:
• Variables
• Commands/Syntax (the way commands are structured)
• Loops
• Decisions
• Functions
Each programming language has a different set of rules
about these features.
Variables
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Variables are part of almost every program.
A variable is a “place to put data” and is
usually represented by a letter or a word.
(Think of a variable as a Tupperware
container with a label on it.)
Variable names cannot contain spaces.
Some programming languages have very
specific limits on variable names.
Variables
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Usually there are several ways to put
information into a variable.
The most common way is to use the equal
sign (=).
X = Y + 7 means take the value of Y, add 7,
and put it into X.
COUNT=COUNT + 2 means take the current
value of COUNT, add 2 to it, and make it the
new value of COUNT.
Variables


Sometimes you must specify the type of data
that will be placed in a variable.
Here are some examples of data types:
• Numeric (numbers of all kinds)
• String (text, “strings of letters”)
• Integer (whole numbers)
• Long (large numbers)
• Boolean (true/false)
Variables

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Variables may be classified as global or local.
A global variable is one that can be shared by
all parts of a program, including any functions
or sub-programs.
A local variable is one that is used only within
a certain part of the program, for example,
only in one function or sub-program.
Commands/Syntax
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Programming languages are truly
languages.
They have rules about grammar,
spelling, punctuation, etc.
You need to learn the rules of a
programming language, just as you
learned to speak and write English.
Loops
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A loop is a repetition of all or part of the
commands in a program.
A loop often has a counter (a variable)
and continues to repeat a specified
number of times.
A loop may also continue until a certain
condition is met (e.g., until the end of a
file or until a number reaches a set limit)
Decisions
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You saw a flowchart symbol for
decisions.
A program often needs to decide
whether something is true or false in
order to see which way to continue.
Programs often use IF (or IF THEN or IF
THEN ELSE) statements to show a
decision.
Decisions
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An IF statement always has a condition
to check, often a comparison between a
variable and a number.
The IF statement also must specify what
to do if the condition/comparison is true.
These instructions (for “true”) may come
after the word THEN, or they may simply
be listed.
Decisions
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In an IF THEN statement, when the
condition is false, the program simply
ignores the THEN commands and
continues to the next line.
In an IF THEN ELSE statement,
commands are given for both the true
and false conditions.
Functions
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In most programming languages, small subprograms are used to perform some of the
tasks.
These may be called functions, subroutines,
handlers, or other such terms.
Functions often have names (e.g., getName
or CALCTAX).
Functions
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A function generally gets information from
the main program, performs some task, and
returns information back to the program.
Functions follow the same rules of syntax,
etc. as the main program.
JavaScript code is primarily made of a series
of functions.
Hints for Writing Code
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“Code” means writing the program in the
appropriate language
Be sure the code is exact (spelling,
capitals/lower case, punctuation, etc).
Write part of the code, try it, then write
more.
Debugging
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To “debug” means to try a program, then fix
any mistakes.
Virtually no program works the first time you
run it. There are just too many places to
make errors.
When you are debugging a program, look for
spelling and punctuation errors.
Fix one error at a time, then try the program
again.
Self-Check

A computer program is…
• A series of instructions to accomplish
•
•
•
something
A TV show
Written in Egyptian hieroglyphics
Can be written any way you want to
Self-Check

A computer program is…
• A series of instructions to accomplish
•
•
•
something
A TV show
Written in Egyptian hieroglyphics
Can be written any way you want to
Self-Check

To “compile” a program means to…
• Translate it into English
• Translate it into binary code
• Pile up the punch cards used for the program
• Run the program as it was written
Self-Check

To “compile” a program means to…
• Translate it into English
• Translate it into binary code
• Pile up the punch cards used for the program
• Run the program as it was written
Self-Check

Pseudocode is…
• The program as it is written in a programming
•
•
•
language
The results of a program that makes secret
codes
The logic of a program written in English
The logic of a program shown in a chart
Self-Check

Pseudocode is…
• The program as it is written in a programming
•
•
•
language
The results of a program that makes secret
codes
The logic of a program written in English
The logic of a program shown in a chart
Self-Check

The flowchart symbol to perform a
calculation is…
Self-Check

The flowchart symbol to perform a
calculation is…
Self-Check

The flowchart symbol to show a decision
is…
Self-Check

The flowchart symbol to show a decision
is…
Self-Check

Look at the flowchart section below. If
the variable X is 5, what will print (K or
1st)?
Print “K”
N
X > 5?
Y
Print “1st”
Self-Check

Look at the flowchart section below. If
the variable X is 5, what will print (K or
1st)?
Print “K”
N
X > 5?
Y
Print “1st”
K will be printed. The answer to the question “Is X greater than 5?”
is NO, since X is equal to (not greater than) 5.
Self-Check

Choose the correct
flowchart symbol for each
of these statements.

AGE>65?

Calc. Tax

START

Print NAME
Self-Check

Choose the correct
flowchart symbol for each
of these statements.

AGE>65?

Calc. Tax

START

Print NAME
Self-Check

A function in a program is…
• Something from trigonometry, like COSINE
• A sub-program, usually performing one
task
• A way to check the accuracy of a program
(a “function check”)
Self-Check

A function in a program is…
• Something from trigonometry, like COSINE
• A sub-program, usually performing one
task
• A way to check the accuracy of a program
(a “function check”)
Self-Check

A variable in a program is…
• A letter or word that represents a place to
store data
• A decision made within a program
• A small sub-program used to find errors
Self-Check

A variable in a program is…
• A letter or word that represents a place to
store data
• A decision made within a program
• A small sub-program used to find errors
Challenge


Try to write pseudocode and create a
flowchart for a program that calculates
the average of three grades and prints
the average.
The word GOOD should be printed only
if the average is more than 80.
Challenge

Possible pseudocode
• Start
• Get three grades
• Average them
• Print Average
• Average>80?
• If Yes, print GOOD
• End
START
Challenge

Get 3 grades
Possible flowchart
• Start
• Get three grades
• Average them
• Print Average
• Average>80?
• If Yes, print GOOD
• End
Calc avg
Print avg
Y
GOOD
Avg>80?
N
END